A memory device called HBM (High Bandwidth Memory) has a structure in which memory chips each having a plurality of channels are stacked. The channels can operate asynchronously and non-exclusively from each other. Because distinct data paths are assigned to the channels, respectively, the HBM can input or output a large amount of data at a high speed.
When an access is requested from a controller to a certain channel in a general HBM, a memory cell array included in any of the stacked memory chips is selected. Accordingly, when accesses are concentrated in the same channel, current consumption concentrates in the same region in the same memory chip, which may result in change of the power potential.